As your galleries do not dynamically resize with the size of the user's browser window, try setting your gallery dimensions in absolute pixel values rather than as percentages.

No. The gallery's actual size on your page should be determined only by the dimensions in the embedding code, regardless of what settings you have used for your Fixed Layout.

I have used your main page and CSS file as a test template and have embedded a gallery directly in the page (rather than externally using widgets) using two techniques (embedding code and an <iframe>) and both galleries display in Firefox and Internet Explorer without any cropping. It looks like the problem is somehow introduced when the widget code comes into play.
Try embedding your galleries using <iframe>s on your widget pages rather than baseURL embedding code to see if this makes any difference.

For example, on this page: http://centerlinedesigngroup.com/Home_f … arkup.html
... change:

<!--START SIMPLEVIEWER EMBED.-->
<script type="text/javascript" src="http://centerlinedesigngroup.com/Gallery/CDGhome3/svcore/js/simpleviewer.js"></script>
<script type="text/javascript">
var flashvars = {};
flashvars.baseURL = "http://centerlinedesigngroup.com/Gallery/CDGhome3/";
simpleviewer.ready(function () {
simpleviewer.load("sv-container", "100%", "100%", "#000000", true, flashvars);
});
</script>
<div id="sv-container" style="background-color: #000000;"></div>
<!-- END SIMPLEVIEWER EMBED -->

... to:

<iframe src="http://centerlinedesigngroup.com/Gallery/CDGhome3/index.html" width="200" height="200" frameborder="0" scrolling="no"></iframe>